CN112034231B - High-frequency current sensor based on frequency-dependent integral resistor - Google Patents
High-frequency current sensor based on frequency-dependent integral resistor Download PDFInfo
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- CN112034231B CN112034231B CN202010706332.7A CN202010706332A CN112034231B CN 112034231 B CN112034231 B CN 112034231B CN 202010706332 A CN202010706332 A CN 202010706332A CN 112034231 B CN112034231 B CN 112034231B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
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Abstract
The invention provides a high-frequency current sensor based on a frequency-dependent integral resistor. The sensor consists of a coil, an integrating resistor and a frequency-variable integrating resistor. The frequency-dependent integral resistor is connected to both ends of the coil. The nonlinear change of the frequency-dependent integral resistance along with the frequency brings remarkable frequency-dependent nonlinearity to the sensor, so that the sensor has very good anti-interference capability, and particularly can resist magnetic saturation caused by power frequency current.
Description
Technical Field
The invention belongs to the field of current signal measurement, and particularly relates to a coil type high-frequency current sensor with remarkable non-linear characteristic along with frequency and strong anti-jamming capability.
Background
In some application scenarios, coil-type current sensors are used to detect current signals on conductors where very strong interference currents are present. For example, when a frequency response method is used to detect the deformation of a large power transformer winding in live operation, a coil-type current sensor is required to detect a weak swept-frequency current signal of 1kHz to 10MHz on a high-voltage outgoing line of the power transformer, and at this time, a power-frequency current of hundreds or even thousands of amperes exists on the high-voltage outgoing line. The power frequency current can not only submerge useful signals in output signals of the current sensor in power frequency interference with huge amplitude, but also can cause magnetic saturation of a magnetic core of the current sensor and lose the capability of detecting frequency-sweeping current signals.
A coil-type current sensor of conventional design, consists of a coil and an integral impedance. The coil is often provided with a magnetic core and a metal shielding shell. The metal shielding shell can shield external electromagnetic interference, but cannot shield interference current on a tested conductor. The integral impedance is generally two types, the first integral impedance is formed by connecting a resistor and a capacitor in parallel and forms resonance with the inductance of the coil, the constructed current sensor is a narrow-band sensor, and the measuring frequency band of the narrow-band sensor is the resonance frequency of the capacitor and the inductance; the second integral impedance is a resistor, and the constructed current sensor is a broadband sensor, which is commonly used to measure high frequency current signals.
The structure of the high-frequency current transformer consisting of the integral resistor and the coil is shown in figure 1, the equivalent circuit is shown in figure 2, and L is the self-inductance of the coil; r is an integral resistor; m is mutual inductance; i all right angle 1 (t) is the measured current; i.e. i 2 (t) is the current in the coil; u. of 1 (t) is induced potential; u. u 2 And (t) is the sensor output voltage. The circuit equation of the equivalent circuit is as follows:
the transfer function H (S) of the sensor is:
wherein U is 2 (S) is u 2 (t) Laplace transform, I 1 (S) is i 1 (t) Laplace transform
Under a sinusoidal steady-state signal, there are:
where ω =2 π f, f is the frequency of the sinusoidal current, U 2 Is u 2 Amplitude of (t), I 1 Is i 1 (t) amplitude.
Therefore, the amplitude-frequency characteristic of the current sensor is:
further, the lower limit frequency of the measurement band of the current sensor is:
it can be seen that when the frequency of the measured current is much lower than the low-frequency cutoff frequency of the sensor, the amplitude-frequency characteristic of the sensor is simplified as follows:
|H(jω)|＝ωM (1-6)
in this case, the amplitude of the output signal of the sensor is proportional to the frequency of the signal, and is a linear relationship.
Specifically, for a current sensor having a lower limit of the measurement band of 1kHz, f l =1kHz, R =6280L. Assuming a measured high frequency current i 1 Is 1kHz, the sensor pair i 1 Output voltage u 2i ＝4441Mi 1 . When 50Hz interference current i exists on the tested conductor r Then, if the magnetic core is not saturated, the sensor pair i r Output voltage u 2r ＝314Mi r . Thus, for high frequency currents i of magnitude of only a few milliamperes 1 In other words, the amplitude reaches the power frequency interference current i of hundreds of amperes r Generated sensor output disturbance u 2r Biu is a ratio of 2i Is ten thousand times larger. Furthermore, for a current i of 50Hz r L inductive reactance ω L =314L, much less than R, i 2r Magnetic potential in the core is much less than i r The magnetic potential in the magnetic core can not be completely counteracted, so that the magnetic field intensity in the magnetic core is very large, the magnetic core is deeply saturated, and the measurement i in a saturation area is completely lost 1 Of the cell.
Disclosure of Invention
The invention provides a high-frequency current sensor based on a frequency-dependent integral resistor, which is characterized by comprising a coil [1], a resistor [2] and a frequency-dependent resistor [3 ]; wherein the resistor [2] is connected with the frequency-variable resistor [3] in parallel to form an integral resistor of the coil [1], and the integral resistor is connected to two ends of the coil [1 ]; the frequency-dependent resistor [3] is a section of metal wire with magnetic conductivity and electric conductivity; the diameter, length, relative permeability and conductivity of the wire are determined by using the existing resistance calculation formula according to the requirement of the sensor on the resistance value of the integral resistor.
The integral resistor R provided by the invention is formed by connecting a conventional resistor R1 and a frequency-variable resistor R2 (omega) in parallel. The resistance of the integrating impedance R is no longer a constant but varies non-linearly with frequency. At a low frequency band, the resistor R2 (omega) is very small, so that the integral resistor R is very small, two ends of the coil are similar to a short circuit, the amplitude of the current i2R in the coil is very large under the power frequency current ir of hundreds of amperes, and u2R is small, so that the interference on the useful signal u2i is greatly reduced. The magnetic potential of i2r and the magnetic potential of ir are counteracted, so that the magnetic core is not saturated; in a high frequency band, the frequency-dependent resistor R2 (ω) is large, so that the integral resistor R at both ends of the coil is similar to the conventional resistor R1, thereby the detection performance of the sensor in the measurement frequency band is not affected by the frequency-dependent resistor R2 (ω).
Drawings
Fig. 1 is a schematic structural view of a coil-type current sensor.
Fig. 2 is an equivalent circuit of the coil type current sensor.
Fig. 3 is a schematic structural diagram of a high-frequency current sensor based on a frequency-dependent integrating resistor according to the present invention.
Fig. 4 is a schematic diagram of an equivalent circuit of the high-frequency current sensor based on the frequency-dependent integrating resistor according to the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and examples.
Referring to fig. 3, a high-frequency current sensor based on frequency-dependent integral resistance is composed of a coil [1], a resistor [2] and a frequency-dependent resistor [3 ]; the resistor [2] is connected with the frequency-variable resistor [3] in parallel.
Coil [1]The magnetic core is annular, the section of the magnetic core is square, the magnetic core is made of an iron-based amorphous body with good magnetic conductivity, the inner diameter of the iron-based amorphous body is 400mm, the outer diameter of the iron-based amorphous body is 440mm, the height of the iron-based amorphous body is 25mm, and the relative magnetic conductivity of the iron-based amorphous body is 2000; coil [1]Is formed by winding a copper enameled wire. The diameter of the copper enameled wire is 0.5mm, the copper enameled wire is uniformly wound on the magnetic core and is wound for 150 turns to form a coil [1]]. Then the inductance L of the coil is equal to 0.021H. For the existing coil type current sensor, when the integrating resistor is only selected from the common 13 Ω resistor (i.e., R) 1 =13 Ω), the transfer function is:
according to the above formula, the low-frequency cut-off frequency f of the sensor l Is 98.6Hz. For a measured high-frequency current signal of 50kHz and 10mA, an output voltage signal u of the sensor 2 Equal to 0.87mv; for a power frequency interference current of 50Hz and 100A, the output voltage u of the sensor 2r Equal to 3.92v, is u 2 4505.7 times higher. Further, the saturation magnetic induction of the magnetic core is about 0.6T, and when the power frequency current reaches 471A, the magnetic core of the coil is saturated, and the measured signal u 2 No longer stable and changes with time (or the degree of saturation of the core).
According to the invention, a frequency-dependent resistor R is produced from a wire made of iron-nickel alloy (assuming that the electrical conductivity is gamma, the magnetic conductivity is mu, the radius is R and the length is D) 2 The resistance R of the length of iron-nickel alloy is then due to the skin effect (i.e., the plunge depth of the electromagnetic field in the conductor varies with the frequency of the electromagnetic field) 2 Can be calculated by the following formula:
let R 2 Equal to 1 Ω at 50Hz, R 2 Equal to 31.6 omega at 50 kHz.
The iron-nickel alloy resistance wire R is connected with a wire 2 Compared with the conventional 13 omega resistor R 1 Parallel connection, for 50kHz, 1Measured high frequency current signal of 0mA, R 1 And R 2 R is equal to 9.2 omega, the output voltage signal u of the sensor 2 Equal to 0.62mv; for 50Hz and 100A power frequency interference current, R 1 And R 2 Is equal to 0.93 omega, the output voltage u of the sensor 2r Equal to 0.28V, is u 2 451.6 times of. Further, the line frequency current when the core of the coil is saturated reaches 1515A. It can be seen that the introduction of the appropriate frequency-dependent resistor R 2 Then, the power frequency interference of the coil type current sensor is compressed by nearly 10 times (4505.7/451.6 ≈ 10), the power frequency saturation current is increased by 3.2 times (1515/471 = 3.2), and the performance of the current sensor is remarkably improved.
Claims (1)
1. A high-frequency current sensor based on frequency-dependent integral resistance is characterized in that the sensor is composed of a coil [1]]And a resistor [2]]Sum frequency transformation resistance [3]Composition is carried out; wherein the resistance [2]]And frequency conversion resistor [3]]Are connected in parallel to form a coil [1]Is connected to the coil [1]]Both ends of (a); frequency-dependent resistor [3]]Is a section of metal wire with magnetic conductivity and electric conductivity, a frequency-dependent resistor [3]]Resistance value R of 2 (ω) is calculated by the following formula:
wherein gamma is the electrical conductivity of the metal wire, mu is the magnetic conductivity, r is the radius, and D is the length; the resistance value of the integral resistor after the resistor [2] is connected with the frequency-variable resistor [3] in parallel is R, and the transfer function H (j omega) of the sensor is R under a sine steady-state signal
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CH355503A (en) * | 1957-12-24 | 1961-07-15 | Ibm | Method for controlling the impedance of circuit elements and circuit element for carrying out the method |
| CN1305085C (en) * | 2004-05-21 | 2007-03-14 | 清华大学 | Metering type electromagnetic current mutual inductor redidual magnetism inhibiting method |
| CN1847861B (en) * | 2006-05-15 | 2010-05-12 | 华中科技大学 | Coil current sensor with magnetic core |
| CN102012448B (en) * | 2010-10-26 | 2012-07-04 | 西安交通大学 | Rogowski current sensor |
| CN104267241A (en) * | 2014-10-20 | 2015-01-07 | 国网吉林省电力有限公司长春供电公司 | High-frequency current partial discharge signal acquisition sensor |
| CN104820128A (en) * | 2015-06-01 | 2015-08-05 | 山东辰祥电气设备有限公司 | Semi-magnetic-core current sensor |
| CN106918628B (en) * | 2017-02-20 | 2019-09-17 | 中国地质大学（武汉） | A kind of non-contacting cement impedance instrument of variable frequency |
| CN207541141U (en) * | 2017-12-04 | 2018-06-26 | 重庆臻远电气有限公司 | High Frequency Current Sensor based on Rogowski coil principle |
| CN108110908B (en) * | 2018-01-23 | 2020-12-29 | 中国矿业大学(北京) | Asymmetric coil magnetic coupling resonance wireless power transmission method |
| CN111044769A (en) * | 2019-12-05 | 2020-04-21 | 国创新能源汽车智慧能源装备创新中心(江苏)有限公司 | Integral residual current measuring method and integrated system |
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